Efficient removal of Cr(III)-carboxyl complex from neutral and high-salinity wastewater by nitrogen doped biomass-based composites

Heavy metals usually exist stably as the species of organic complexes in high-salinity wastewater. Therefore, their effective removal is challenging, especially when the initial pH is neutral. Herein, a novel nitrogen doped biomass-based composite (N-CMCS) was synthesized to remove the complexed heavy metal of Cr(III)-carboxyl. The maximum adsorption capacity of Cr(III)-Citrate (Cr-Cit) by N-CMCS under neutral pH (7.0) and high-salinity (200 mmol/L NaCl) condition was up to 2.50 mmol/g. And the removal performance remained stable after 6 times of regeneration. Combined with species and characterizations analysis, electrostatic attraction and hydrogen bonding were the main mechanisms for N-CMCS to remove Cr(III)-carboxyl complexes. Dynamic adsorption indicated N-CMCS column could treat about 1300 BV simulated wastewater and 350 BV actual wastewater with the concentration of effluent lower than 1.0 mg/L. Furthermore, N-CMCS could remove a variety of complexed heavy metal ions under neutral pH, indicating the great potential in practical application.